Energy and communication transmission cables are susceptible to damage by many different means, including puncture by shovels, trucks and other equipment, plus bullets, arrows, and other projectiles. Cables are designed to resist such damage using thick insulating plastic layers, metal armor layers, and the like. One design is double or multiple layering of insulating and/or protective coatings about a conductive element such as those taught in U.S. Pat. Nos. 4,789,589, 5,841,072 and 7,105,749. Another design comprises polymer-coated metal shielding and armoring products such as ZETABON™ metallic armor products available from The Dow Chemical Company. One variation on this design is the replacement of the metal layer with a foamed polymer layer, e.g., a foamed polypropylene layer.
Still another design is the use of a buffer tube containing a thixotropic, water-blocking gel such as that taught in U.S. Pat. Nos. 6,714,707, 6,496,629 and 5,505,773. Yet another design is the use of a grease composition as a cable filling material such as that taught in U.S. Pat. No. 5,433,872. These grease compositions comprise a polyol having a molecular weight of at least 4,000 and an agent, e.g., colloidal particles, that imparts thickening to the polyol. US Patent Application Publication 2004/0063812 A1 teaches a cable filling material that is a dispersion of microspheres and a gel comprising an oily base and an organic polymeric gelling agent.
As effective as these existing damage-resistant technologies are, more effective systems are desired. Repairing and/or replacing damaged cable is costly and time-intensive; the costs and inconveniences associated with the loss of use of a damaged cable can be substantial; and the human injuries and property loss that can be incurred from damaging a cable, e.g., a high-energy power cable, can be terrible. Consequently, the ability to incorporate into a cable design a free or bound material that shows extreme resistance to externally applied forces would be a considerable advance in the cable protection art.